An example of a unit of this type is described in EP 0 645 875.
Among the conditions which must be satisfied by these electro-hydraulic units, can be cited minimum size, sealing against external moisture and the cost of production.
The present invention has principally for its object to propose an electro-hydraulic unit whose size is substantially less than known units of the prior art.
It is for example already known, from FR 2 710 699, to position the electric motor and the electronic control in a same and single housing. However, the housing thus made has even greater size, because each portion is juxtaposed or inserted in another but retains all the same assembly of the usual components.
There is also known from EP 0 769 437 an electro-hydraulic unit in which, to reduce the number of parts, there is provided a ferrocircuit common to the winding (of the electrovalves) and to the stator (of the motor). However, this ferrocircuit is made by assembly on the one hand of the rear portion of the cover of the motor and on the other hand by the hydraulic block itself. It is thus a matter of a common ferrocircuit but made in two separate parts. According to this document, the hydraulic block is at least magnetizable as to its winding. However, it is not disclosed how to render magnetizable the hydraulic block.
In fact, two solutions are possible to have a magnetized hydraulic block: either the block is made of iron, or magnetic elements are added to it. The production of a hydraulic block of iron is unthinkable without substantial increase of cost. Thus, such a block is too long and too costly to machine. This is moreover the reason for which the hydraulic blocks known at present are made exclusively of aluminum. Aluminum is thus a metal which can be easily machined and above all rapidly, with conventional tools. However, given the shape and complexity of present hydraulic blocks, it is not conceivable to make them by molding.
On the other hand, it is much too costly to add either a magnetic material or a magnetic element inserted in an aluminum hydraulic block to render it magnetic. These techniques are too troublesome.